Algorithms behind load-balancers?

Question

I need to study about load-balancers, such as Network Load Balancing, Linux Virtual Server, HAProxy, etc. There're something under-the-hood I need to know:

• What algorithms/technologies are used in these load-balancers? Which is the most popular? most effective?

I expect that these algorithms/technologies will not be too complicated. Are there some resources written about them?

Answer 1

Load balancing in Apache, for example, is taken care of by the module called mod_proxy_balancer. This module supports 3 load balancing algorithms:

• Request counting
• Weighted traffic counting
• Pending request counting

For more details, take a look here: mod_proxy_balancer

Answer 2

Not sure if this belongs on serverfault or not, but some load balancing techniques are:

• Round Robin
• Least Connections

I used least connections. It just made the most sense to send the person to the machine which had the least amount of load.